Apparatus for manufacture of piezo-electric elements



Dec. 16, 1952 c. CHILOWSKY 2,621,624

APPARATUS FOR MANUFACTURE o? PIEZOELECTRIC ELEMENTS 5 Sheets$heet 1 Original Filed Jan. 29, 1944 fig INVENTOR.

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AT TORNEKS APPARATUS FOR MANUFACTURE OF PIEZOELECTRIC ELEMENTS Sheets-Sheet 2 Original Filed Jan. 29, 1944 mm m Y [Ill/I m. M Q my m F Wk r R wr/llWl/rfllill M Tn QN mw Q m MW Dec. 16, 1952 c. CHILOWSKY 2,621,624

APPARATUS FOR MANUFACTURE OF PIEZOELECTRIC ELEMENTS Original Filed Jan. 29, 1944 5 Sheets-Sheet 3 w Z. Z

IN V EN TOR.

ATTORNEYS \m m km Wm wm BY WW MFM Dec. 16, 1952 c. cHlLowsKY APPARATUS FOR MANUFACTURE OF PIEZOELECTRIC ELEMENTS 5 Sheets-Sheet 4 Original Filed Jan. 29, 1944 INVE\NTOR.

ATIWHZWS' Dec. 16, 1952 c CH K I 2,621,624

APPARATUS FOR MANUFACTURE OF PIEZOELECTRIC ELEMENTS 5 Sheets-Sheet 5 Original Filed Jan. 29, 1944 IN V EN TOR.

Patented Dec. 16,1952

APPARATUS-FOEMANUFAGTURELOF-PIEZO= ELECTRIC ELEMENTS Constantin Chilowsky, .New.-Y ork,. N. Y.

Original applicationJJanuary 29 ,1944,-- Serial No. 520,275.; Divided and this application July-19,

1948,iSeria1,No. 39, 385

9 Claims.

This invention. relates to .the manufacture; of piezo-electricelements, and particularly to apparatus for regulating andadjustingthe natural frequency of. piezo-electric stabilizers, having: mechanical resonance. for. high frequency electric circuits. This applicationisa; division of copendingapplication. Serial No. 520,275, filed January 29, 1944,.issued as Patent No. 2,445,-310, dated July .20, 1948 Stabilizers. with mechanical resonance, and particularly piez -electric ,quartz plates,- whichoscillate. transversely, through. the directionof thickness require an extremely fine adjustment of their thickness. Usually the first app foximate adjustment is relatively ,simple, I consisting of amechanicalgrinding treatment; The second; adjustmentis also usually performed with the aid. of. agrinding machine,- but under periodiccontrol by the operator. for checking the natural frequency. of .the-crystal plate. The final I or. third adjustment-is the most delicate and1-pre-- cise, and is performed generallyby manual" grinding. under constant control of. the natural frequency or of .thecdifference between j the -natural frequency and the required frequency. 1 According ,to the present invention,;., it, is proposed to substitute, atleastfor the .second and third operations, anentirelydifierent procedurewhich is much:.-more rapid andwl-iich,- ifenecessary,v can be. madeentirely automatic.

According to this procedure, plates of piezoe electric quartz =are finished by the first. grinding operation ,to a.,thicknessless than the required final thicknes,s,,and consequently for higher natural oscillations. The quartz laminations; or plates are thenbuilt ,up to-the requiredthickness by progressively depositing a layer of substance which firmly adheresto the surfacespfthe laminations or plates and increases their thickness, while reducing their. natural period of oscillation until the required value is reached. Suchan adherent, layercan. be gradually, deposited, for instance, by cathodic pulverization, I but this in-v V vention provides particularly fora procedure of: depositing metalby vaporizationin awery high vacuum, this process being specially adapted and particularly advantageousifor, this particular purpose.

In carrying, out this procedure aquartz lamination .or plate (for. instance, after the, first grinding operation) isplaced inlfront of-andat a certain distance from the materialto beadeposited, which latter is. maintainedby electric heating at a temperature sufiiciently high for its vaporization, the entire assembly being containedin a hermetically sealedchamber-in which high, vacuum ismaintained. Metallic-or other vapors, in a molecular form, are; projectedthermally in straight pathsfrom. thei1' sourc:e t against the surfacesof-the laminations at a; high-speed-through the vacuum and addtothe surfaces strongly; adhering molecular layers These layers: are deposited. gradually and uniformly at a rate which, can ,be-varied-within wide limits by varyingthe temperature ..of wthe. deposited. material, 1. e., of the source .of .-.vaporization. V

The ,natural. frequency of mechanical; 0scill a,-- tions of the. resonance of. quartz;plates yaries, gradually as a .function of the thickness of the deposited layer,- and. it. is proposedto. placelthe plate in front of arsource of. vapor in .anelectric, system which will start andsmaintain mechanical, oscillations of the lamination during-the de-, positing of the. addedmaterial. Electric wires of the system ,pass.. -to,theoutside of themplate and place it ina condition. ,under which it,.will be possible to. determine the natural. frequency of the quartz. As soon asthis frequency-reaches the required value, the process, of. deposition of; thematerial is stopped; this beingaccomplished, for instance, by removal of the quartz or..by screening it ,fro1n the .source, of vaporization so as. to protect it from the, vaporsk Various, metals can. be used to, ,constibfltdthe added material, such. as aluminum, copper, silver, nickel,. gold platinumy chromium. etc, a and j the, same process, of. vaporization, inf. a vacuum can also be used withnonemetallicsub,. stances, It is preferable to ,select. such .mate,-,. rials as willtproduce the least, possible reflection,. of mechanical vibrations in. their, passa ev from, the quartz .into the deposited layer. For this purpose the material should. be, so selected that. the productof-its density d1 .,and thevelocity yr of, propagationof sound, inthe. material isfas close as possibler o ,the. productof the density doof. quartz and thevelocity V0.0f sound-.propagation therein. It is particularly desirable to -use forv the formation of=,added ,layers aluminum whose product d1 v1 is very closeto theproduct do No, of; quartz. Stillbetter results .maybeiob tained by using} alloys of aluminum or copper-- (or other metals) or-by .using. meltedquartz The latter has the advantage of stilllower reflece tion, as well asavery small coefficient of damp,- ing of 'vibrationsranda very low. temperature c eificient, so that its properties, areafiected very,v little by variation in; temperature; On the other; hand, layers of very dense metals such as gold or platinum (or other alloys) can be used for providing (in layers much thinner than the aluminum) not only adjustment of frequency but also complete stability against the action of external agencies. In this connection it may be noted that layers which are very thin in relation to the thickness of the quartz plate have very little effect on the damping of oscillations or on temperature variations.

Generally speaking, the thickness of the deposited layer is of the order of the accuracy with which the lamination is finished during the first mechanical grinding operation. According to the procedure of this invention, however, it is possible considerably to reduce the requirements for accuracy of this grinding operation, which is thereby simplified, with a corresponding increase in thickness of the deposited layers when necessary.

For industrial purposes it is proposed to treat simultaneously a more or less large number of quartz plates or laminations in a single operation. Simultaneous depositing of the material on a large number of quartz plates is possible but simultaneous control for a large number would be difficult, and it is therefore proposed that the plates should be treated successively in a single operation of the apparatus, the plates being placed successively in front of the incandescent source from which a jet of vapors is directed. At the same time the plate on which the vapors are being deposited is connected with wires which extend outside the apparatus and which are connected with instruments for continual measurement of the natural frequency of mechanical os- I cillations of the plate. The frequency measuring apparatus may comprise known devices such as an oscillator of mechanical resonance in a quartz plate of a constant natural period of frequency and preferably of the same frequency as that which is desired for the quartz plate being treated. The arrangement is preferably such that it will be possible at all times to compare beats between the two frequencies, one produced by the control plate outside the vacuum apparatus and the other (constantly changing with the deposit of additional material) by the quartz being treated.

Observation of these beats can be maintained by the operator, as by means of a telephone, or by a suitable apparatus for visibly indicating the beat frequency. It is particularly provided, however, that the control may be effected by an automatic apparatus which will stop the flow of the vapors to the surface of the quartz plate at the exact moment when the latter has been built up to a thickness such that the beats become zero or their predetermined value. Suppression of the flow or stream of vapor may be effected by the removal of one plate and substitution of another in front of the source of vapor; or if greater accuracy is required, the stream or jet of vapor may be stopped by closing automatically a shutter which remains closed only long enough to permit replacement of the treated plate by another one. Such instantaneous cutting off of the vapor stream insures great precision.

Preferably a large number of quartz plates are introduced into the apparatus at the same time, the number depending on the size of the apparatus and being, for instance, several hundreds or even thousands of pieces. The speed of deposition is so regulated that the plates will have time to be treated successively, while each treatment will be sufficiently long to make possible the accurate regulation of the natural frequency of the quartz by stopping the deposition at exactly the right point.

In order to realize the last condition, the quantity of material projected on the plate per second should be relatively large at the beginning of each operation and gradually decreasing as the natural frequency of the plate approaches the required value, thereby making possible very accurate regulation of the time of stoppage of the deposition. Assuming that the intensity of the vapor source remains the same, this effect may be obtained by shielding the stream of vapor, shielding varying as a function of the difference in beats between the two frequencies; the shielding increasing and the amount of material deposited being reduced with the approach to the required frequency. The shielding may be made continuous or step by step, as by the successive introduction of smaller and smaller diaphragms. Under such conditions of regulation, the average rapidity of deposition may be regulated in such a manner that the treatment can be completed in thirty to sixty seconds, for instance; although this time may be varied within wide limits according to particular requirements.

A sufficient amount of material should be provided at the source of vaporization for uninterrupted continuance of the operation which may require several hours. If desired, it may be possible to treat simultaneously several pieces of quartz, using the same source of vapor or different sources, and with different frequency measuring installations.

The process of deposition of vapors in vacuum affords considerable advantages over the process of deposition by cathodic pulverization, particularly in that the speed of deposition is much greater, thus permitting successive operation on a large number of quartz plates or crystals, there is better adhesion of the is possible to use aluminum which cannot be used in the cathodic method.

The herein described process affords considerable technical advantages, including:

1. Saving in time of the operation, since the natural frequency of the plate may be regulated and corrected in less than one minute.

2. Successive accurate operation on a large number of quartz plates in a single operation. if 3. Automatic control of such successive opera- 4. Regulation and correction of thickness can be made with greater precision than with manual operation, which is especially important for extremely high frequency.

5. Quartz plates which have already been mounted for use may be treated in the vacuum chamber, so that subsequent correction of the frequency is not necessary.

A practical embodiment of the invention is shown in the accompanying drawings in which:

Fig. 1 represents a vertical median section of the vacuum chamber and associated parts, parts being broken away.

Fig. 2 represents a partial transverse section taken along the line IIII of Fig. 1, looking in the direction of the arrows.

Fig. 3 represents a detail elevation of the intermittent driving mechanism shown in Fig. 1.

Fig. 4 represents a horizontal section taken along the line IV-IV of Fig. 1, looking in the direction of the arrows.

Fig. 5 represents a detail vertical section of a modified form of vaporizer.

deposited layers, and it 2&5813534:

iestrep, esemss..ini verticaisecti n. ,p r ss ea ing broken: away; a mQdifiedIaITran em nt pt. the; intermittent drive.

Fig. 7 representsasectionthrough the; cylinder and vacuum chamber, in a plane perpendiculartotheaxis-of thecylinder, showing ,a modified form of driving means for the :cylinder.

Fig- 8 represents a detail *elevation ,of a part :of the cylinder,- showing. a. particular means. for mounting quartz plates thereon.

Fig. 9 represents, in: plan view, a modified means-,formounting "crystal plates ,on the vcylinder.

Fig. lurepresentsa sectionztaken along the line XX .of' i Fig. 9, looking in the. direction of the" arrows- Fig. 11.represents,- in plan view,,another modified. means for mounting. crystal plates on the cylinder.

Fig. 12 .represents a sectiontaken along the line" XIL-XIIof. Fig. .11, looking inthe direction of the. arrows.

Fig. vl3 represents a plan view of a modified form of the attaching means shown in-Figs. l1 and 12.

Fig. l lrepresents adetailsection in a plane perpendicularrto theaxis of-the cylinder, showingrarform .ofcontactor.

Fig,.15,represents a, section taken along the lineXV-XVofFig. 14,, looking in-the direction of the/arrows.

16 represents a longitudinal section throughsa modified-form of cylinder; parts being. broken :away;

Figs. 1'7, 18 and 19 represent, in section, modifiedmeans for mounting plates on the cylinder shown in-Fig. 16; Fig. 20 representing a top plan view-of thetholding means shown in Fig. 19.

Fig... 21 is a wiring diagramrepresenting the circuitswhich may-be used for precise automatic. control of the deposition of metal on the plates being treated.

Fig. 22isa. wiring, diagram representing a modified circuit arrangement;

Fig. 23 represents avertical section through a quartz plate :showing a-modified arrangement for mounting it on a support on the cylinder; Fig. 24 representing a plan view of saidsupporte Fig. 25 represents a detail vertical section showingthearrangement of,.a pivoted contactorand adjacentparts.

Fig. 26represents5a sectiontakenalong the line Fig. 31 represents a. detailhorizontal" section of the shutter shown in Fig. 27, taken along the line XXIH-XXXI of said Fig. 27.

Fig. 32 represents a detail vertical section showing means for ascertaining the accuracy of thenatural frequency of a crystal plate.

Fig. 33 representsabottom planview of the device shown in Fig. 32, parts of the, vacuum chamber v being. removed; and

Fig. 34.1'epresents adetail vertical se,ctionaof at;

modifiediorm of theeelementrzshown ini'Flgsz- 32 Referring. to, the drawings, and particularly Fig; ,1 thereof,,.there, is shown a high vacuum chamber 1 containing... a. hollow metallic i cylinder} adapted tosupport on itsxouterrsurface-a multiplicity of. quartz :plates 3, which: plates may;- preferably; be arrangedspirally:around. the: cyl inder. The chamber! istraversed by ashaft' l provided with threadsof largefpitch; which shaft 1 serves as the axis .of rotation and axial -tdisplace-'-- It: will1be understood that the; axial displacement of the cylinder should correspond to the spiral arrangement of the plates on thesurface thereof. Thecylinderlis mounted .by means -:of a cross.;bar 5 ion a..nut' fitwhich enga es-with .thethreads' on the: shaftal, thecylinder beingguided axially .byxmeans .of the. nut 6 anda bushing 'l' whichisiofaassize suffi cientto. extend over at, least .two threads of i'th'e-' screw'and whichisrconnectedsto the cylinder by means of a cross-barsimilarto the bar 5.v The.

mentof the cylinder 2.

screw 4 is shown as being rigidly mounted on the covert-ofthe vacuum chamber and havingits...

inner end supported .byia bracket Qprojecting inwardly from the body of said chamber.

Since it is desirable that'complicated operat more readily be-keptclean. The'cover 8 is fitted to the body of the vacuum chamber witha tightly, sealed joint, and the CODIIGCtiOIIi-tO: a vacuum pump is indicated at Ill.-

The vacuum-chamber is provided. with awindow II in the diagram l2 communicating wi,th.a source of metallic vapor and the quartzplates 3, spirally mounted on they cylinder 2, are successively brought in position in front of the window II by the rotation and axial movement of said cylinder. by meansof the gear ring 13 (composed of magnetic material such as soft iron) whichring is.

fixed to one end of the cylinder '2. Theprojectingteeth of said ring I3 are magnetically engaged by a. system of magnets having cores l4 and windings l5, which magnets form a complete or partial spiral ringaround the-outsideof the por-' tion I 6 of the wall of the chamber. This portion lfi-is providedwith spiral tracks I! having the, same pitch as the threads of the screw 4. The magnets [4,15 are supported in a ring :18 having;

gear teeth [9 around its periphery; the-teeth l9 engaging the teeth of a wide gear 20, bywhich the magnet ring, assembly may be rotated and advanced along thespiraltrackll. During such rotation of the magnets, by their attraction for the projecting parts of the ring l3, will move said ring and the cylinder 2 around and along the screw-4 simultaneously at the same rate.

Theparts just described are driven intermittentlylby means of amotor 2| connected-by wormgearing 22 with .the shaft of the wide gear 20. On the same. shaft is mounted aidisk 23 having-regularly'spaced slots in its periphery, the slots being so disposed that rotation between twoconsecutive slots corresponds tothe rotation of the cylinder which is needed to move a quartz plate from itsposition opposite thewindow II and to movethe next following quartz plate-into such position.

A magnet 24 operates a pawl 25 which engageswith;:the:slots inthe disk 23 for locating the 'partsdmstationary positiomand which' may-be;-

The cylinder is driven magnetically.

disengaged to permit rotation of the cylinder. These parts are shown in detail in Fig. 3, which shows also the contacts 26 for energizing the motor 2| when the pawl is moved to releasing position in order to permit the disk 23 to be rotated until the pawl engages the next slot. The magnet 24 is provided with electrical connections A, B which may be connected to a source of electric current thorugh a manual or automatic switching arrangement. In the case of automatic operation, the contacts A, B are connected with the final relay of a system in which the circuit is closed automatically when the quartz plate in front of the window i I has reached the desired thickness corresponding to a desired frequency. At that moment the relay will send to the magnet 24 a short impulse of current sufiicient to free the pawl 25 from the disk 23 and to cause the motor 2| to be operated by closing the contacts 26; the impulse being sufliciently brief so that the pawl will fall into engagement with the next slot under the urging of a spring, not shown.

When the accuracy required in the final product is not too great, it can be attained merely by moving the quartz plates successively into and out of a continuous jet of metal vapor. In order to achieve more accurate results, however, it is desirable to control the jet of vapor by means of shutters which can be operated to turn the jet off or on in a small fraction of a second. Such shutters are shown at 2'1, 23 in Fig. 1, the shutters being of magnetic material, mounted on hinges and arranged to be normally closed, as by the action of gravity. The shutters 21, 23 are in the field of a coil 29 and may be opened instantly upon the passage of current through said coil. By means of suitable wiring, not shown, the current through the coil 29 may be interrupted to close the shutters during the time that the pawl 25 is out of engagement with the slots in the disk 23 and while the motor 2! is acting to move a treated plate out of its position before the window II and to move another plate into position for treatment; the coil 2 being arranged to receive current and open the shutters as soon as the new plate is in position.

The vaporizer for the metal to be deposited (aluminum, for instance) is shown at the bottom of Fig. 1 wherein the metal 353 is contained in a crucible 3! (of tungsten, molybdenum, carbon or graphite), the metal 30 being suflicient in quantity for the treatment of all the quartz plates on the cylinder 2. The crucible Si is contained with in a fused quartz tube 32 having flanges at its top for tight engagement with the vapor inlet passage of the vacuum chamber. The crucible ii is preferably formed with the upper portion of its walls reduced in thickness, and is provided at its top with outwardly projecting hooks or flanges 33 for engagement with the inwardly projecting flange 34 of a tube 35 supported from the top of the tube 32. The crucible 3! may also be provided with projections 35 for insuring proper centering of the crucible in the tube 32. The supporting tube 35 should be readily removable for cleaning or replacement, since it is intended to collect on its surface any excess of metal vapor resulting from the expansion of the jet; such cleaning being effected by washing in nitric acid, for instance, for dissolving the deposited aluminum. The inner surface of the tub-e 32 should be silvered as shown at 3? in order to form a mirror facing the crucible, so that thermal radiation from the latter will be reflected and the tube 32 will not become overheated. The mirror 31 is preferably cut into separate surface areas so that it will not be appreciably heated by induction within itself. The high vacuum maintained within the apparatus, including the vaporizer, insures a minimum of heat loss by convection. The metal 30 is heated by induction upon the passage of high frequency currents through the coil 38.

A plurality of coils 39 may be provided around the upper part of the crucible 3|, these coils being supplied with high frequency currents which are progressively shifted in phase from top to bottom so as to form a sort of rotating field which will act on the metal as an electrodynamic focre directed from the top to the bottom. This force will tend to drive back into the mass 30 of the metal any vapors which may have condensed on the upper walls of the crucible. The size of the vapor jet may be regulated by means of the removable metal cone 40 (of tungsten, for instance) which is located within the field of the coils 39. The provision of said coils is particularly useful when there is danger of an accumulation of deposited metal vapor partially closing the opening of the cone 40.

In the modification shown in Fig. 5, the coils it are replaced by a single coil 4!, so positioned in relation to the cone 42 and the crucible 43 that the latter are in an alternating magnetic field which decreases toward the lower part of the device. When the coil 4| is supplied with current at a suitable frequency an electrodynamic force will be created, acting in a downward direction on any metal which may have been deposited on the inner walls of the cone 42 and the crucible 43.

In the modified form of the cylinder and vacuum chamber shown in Fig. 6, the successive positions of the cylinder may be regulated with great precision. In this case the cylinder 44 (supported as previously described) is provided with a spiral rib 45 having transverse grooves 16 at regular intervals along its length, said grooves being spaced a distance equal to the distance from center to center of successive quartz plates 3. The quartz plates are arranged spirally around the cylinder in the space between successive turns of the spiral rib 45. In the wall of the vacuum chamber 4'! is fitted a flexible membrane 48 having a, finger 49 projecting inwardly from its center and adapted to engage intermittently with successive grooves 46 in order to stop the rotation of the cylinder. The finger 49 may be moved out of engagement with a groove, to permit rotation of the cylinder, by means of the eletcromagnet 50 acting on the end 5| of a lever 52 which is hinged to the outside of the chamber at 53 and is connected to the outside of the membrane at 54. A short current impulse on the magnet 50 (through the leads A B may be simultaneous with the current supplied to the magnet 24 (Figs. 1 and 3) so that the cylinder will be released for rotation at the moment when suilicient metal has been deposited on the plate being treated. While the disk 23 and pawl 25 may serve to stop the cylinder in a reasonably accurate position, it will be evident that the arrangement shown in Fig. 6 insures a much more precise location of the plates in the desired position.

In Fig. 7 is shown a modified driving means for rotating the cylinder, in which the cylinder is entrained by the rotary field of a number of magnets 55 and their coils 56 which are placed circumferentially around the vacuum chamber. The cylinder may be rotated by providing the magnetswith arelatively-short impulse of alternating current at the moment when the treatment of a plate has been completed and a new plate is tobe brought into position. This method of driving'the cylinder may desirably be combined with the stopping arrangement shown in Fig. 6.

The quarts plates may be attached to their supporting cylinder in a variety of ways. As shown in Fig. 8, the plates 3 are secured by means of a suitable glue or other adhesive to the ends of a series of small projections 5'! which are placed in groups of four so as to support the plates'at their four corners and at a height sufficient'to keep the plates from comin in contact with the cylinder.

As shown in Figs. 9 and 10, the cylinder is provided with a series of small permanent magnets 58, the cylinder itself being preferably made of magnetic material. A small cap 59 of insulating' material such as porcelain is provided with an iron insert 60 and is adapted to fit loosely over the upper end of the magnet 58. The surface of'the cylinder is formed with raised ribs 6I- around each of said magnets in order to support the four corners of the plates 3; the plates being held in position by means of the caps 59 due-to the attraction of the magnets for the iron inserts 68 in said caps. Figs. 11 and 12 show a modified form of magnetsBZ in which the supporting ribs constitute part of said magnets; the caps being removed in these figures. A more precise positioning of the quartz plates may be insured by the arrangement shown in Fig. 13, in which the magnets 63 are cut out at 64 to provide-recesses for receiving the corners of the plates.

Figs. 14 and 15 show a form of contact finger B5'mounted'on an insulating support 66 inside the vacuum chamber in a position such that it will makean electric contact with the metal deposited on each quartz plate as it is being treated. The contact finger 65 is suitably connected with a' source of high frequency current in order that the-natural frequency of the plate may be determined during its treatment.

The modified form of cylinder shown inFig. 16 comprises concentric cylindrical walls 61 and 68, hermetically welded or soldered together around their ends 69. The inner wall 61 is preferably of a magnetic material such as iron or steel, while the outer wall 68 is of a non-magnetic material such as stainless steel, the inner wall "being substantially thicker than the outer wall. In' the cylindrical space between said walls ismounted a'number of permanent magnets having their -magnetic'poles disposed radially of the cylinder, the polarity ofevery other magnet being reversed as indicated in the drawing, and the magnets-being disposed at intervals corresponding to the points on the cylinder where quartz plates are to be mounted. The magnets may be held in their proper positions by a filling H of a solidified plastic material. The use of such a system of magnets has the advantages of providing a relatively smooth surface on the cylinder so that it can readily be kept clean, and the-external magnetic field can be made as strong as desired, for instance, by reducing the inner diameter of the wall 61. The plates may be mounted on the cylinder shown in Fig. 16 by such means as are shown in detail in Figs. 17 to 20. *In' Fig. 1'7 thegplate 3' is slightly beveled and isheld-ina steel tray 12, theedges of whichare arranged-toclampthe beveled edgesof the plate.

The :bevelededges may loe replaced by: narrow fingers, in which case the plate need only be beveledv at points correspondingto the position of said fingers, as at' the four corners of the plate. The cylindrical Wall 68 may beprovided with spiral projections serving as'a guide in the positioning of the trays 12, which can be made of sizes and shapes to fit various sizes and shapes of quartz plates. In Fig. 18, the wall 68 is provided with projections 13 on which'the plate supported and to-whi'ch it is held'byth'emagnetic attraction of a steel frame 14 which surrounds the plate and engages its corners as shown in Fig. 20. A simpler form of frame is shown at 15 in Fig. 19, this frame having'the same appearance in plan view as the frame 14 shown in Fig. 20. The frames "and 15 may have current appliedto them for testing the frequency of the plate as previously described.

Automatic regulation and control of the natural frequency of the quartz plates during their treatment may be effected by the provision of a heterodyne hook-up in which there the two oscillating circuits, one controlled by a standard quartz crystal and the other'controlled by the quartz plate being treated. This produces an alternating current the frequency of whichrepresents the difference between the frequencies of the two'pieces of quartz, i. e., a beat frequency. It is possible, for instance, to apply to two control grids of a mixing radio tube,'the two oscillating currents controlled respectively by the two pieces of quartz,'a filter of low frequencies (below 1,000, for instance) at the exit from the mixing tube will-pass only the best'frequencies. The current thus produced may be used for operating a series of relays tuned to frequencies of 100, 10 and 1, for instance, or for operating a series of nonselective relays which are connected through low frequency filters with limits of the same three frequencies. Such relays, operating'successively, can first reduce the rapidity of deposition of metal on the plate being treated, and then stop such deposition entirely when the proper "frequency has been reached. A low frequency am plifier may desirably be used between the mixing tube and the relays.

The'wiring diagram of Fig. 21 illustrates the foregoing arrangement, in which the quartz plate being treated is-sh0Wnat 18, connected in the oscillating circuit 19 having the tube 80. The standard or controlcrystalfll is connected in a similar circuit 82 having'the tube 83. Thefrequencies derived from the circuits [8 and 82 are applied'to the grids of the mixing tube 84 in'the circuit 85. The beat frequencies thus produced in the circuit 85 are amplified by the lowfrequency amplifier 86 and are passed to the relays 81, 88, 89 having mechanical resonance,"their respective vibrating blades 90, 9|, 92 being arranged to resonate'atfrequencies of, for' instance, 1, loand 100 respectively.

In ordinary'cases when very great precision may not be required; it may suffice to operate only the single relay 8'! having the blade 90. This blade will close the contact 93 so .as tosendcurrent impulses from the battery totheterminals A, B of the magnet 24. (Fig. 3), .thus controlling the stopping of deposition of metalon the plate being treated and permitting movement of the cylinder to bring a new plate into position fortreatment. Whengreater precision is re quired, the re1ays'8l, 88;.89 may be operated, the relay 89 operating its blade 92 at a frequencyof 100 inorder'to'close the contact 95 in the circuit of an electro-magnetic device which places a smaller diaphragm in front of the window of the vaporizer. In a similar manner, the relay 88 will respond to a frequency of 10 to close the contact 9| in order to place a still smaller diaphragm in position, so that metal is deposited more slowly on the plate as its frequency approaches the desired value; when this value is reached the relay 8'I, responsive to the beat frequency of 1 will stop the deposition and move a new plate before the window as previously described.

In the modified arrangement shown in Fig. 22 the resonant relays 81, 88, 89 are replaced by low frequency filters 96, 91, 98, the filter 91 being adapted to pass frequencies of the order of 100 cycles per second and being associated with the high resistance relay 99. This relay is adapted to close the contact I in a secondary circuit which operates an electro-magnetic device for reducing the size of the diaphragm as explained in connection with the relay 89 of Fig. 21. The filter 91 may pass only frequencies below and thus operate the relay IOI to close the contact I02 for further reducing the size of the diaphragm, as in the case of the relay 08. The filter 98 may pass only frequencies below one cycle in order to operate the relay I03 to close the contact I04 in the circuit of the terminals A, B, thus stopping the jet of vapor and moving a new plate into position for treatment.

Special care must be taken in establishing electric contact with the metal layer deposited on the quartz plates, in order to avoid short circuiting of the testing and control circuits. Thus it is important that the deposited layer be prevented from coming in contact with any grounded part of the plate support, as noted in connection with Figs. 9 to 13 and 16 to 20. A preferred arrangement for obtaining electric contact with the deposited metal while it is being deposited includes the provision of a movable contact which may be caused to touch the deposited metal after the treatment has started. The contact finger shown in Figs. 14 and may be used to establish contact with the deposited metal by providing for a slight rocking motion of the cylinder in each of its fixed positions. In such a case the metal may be deposited first on parts of the plate which are not touched by the contact finger 65, and the cylinder then rocked slightly to bring the deposited metal in contact with said fingers while the depositing of the metal is continued and completed. Such rock ing motion could be provided for in the structure shown in Fig. 6, for instance, by making the grooves 46 slightly wider than the end of the finger 49 which engages them.

An alternative form of contact is shown in Figs. 25 and 26 in which a contact finger I05 is mounted on a lever I06 which is pivoted at I01 on a support I08. A resilient contact I09 is mounted on the opposite end of the lever I05 in such a manner that it will bear against the end of an electrode I I0 which is mounted in and insulated from the wall of the vacuum chamber; the electrode IIO being connected to an external lead wire III. The contact between I09 and H0 is made when the lever I06 is rocked to brin the contact finger I05 against the layer of metal deposited on a plate 3, the lever being moved to this position by the action of the coil II2 on the iron core H3. The finger I05 may be moved out of contact with the deposited metal by the spring action of the resilient contact I09 when current through the coil H2 is interrupted, or a separate spring may be provided for this purpose.

A modified form of vacuum chamber is shown in Figs. 27 and 28, in which the quartz plates are placed in a circle near the periphery of a disk II5 provided with openings II 6. The openings may be beveled to fit correspondingly shaped plates as shown in Fig. 30. The disk is arranged for rotation on its axis Ill and may be driven by the magnetic engagement between teeth IIO on the periphery of the disk and the teeth II9 of a magnetic device which, in turn, is driven intermittently by a motor or the like, not shown. The latter device includes a coil I20 surrounding a core I2I, and the teeth I I9 are arranged as shown in Figs. 27 and 28 so that adjacent teeth alternate in polarity according to their connection with the top or bottom of the core I2I.

A rotary shutter I24 is arranged for magnetic control through the wall of the vacuum chamber by means of the three interconnected magnets I 25, the position of the shutter being determined by the distribution of current in the windings of said magnets. The shutter is provided with an opening I26 to permit passage of vaporized metal when the opening is in register with the jet of such vapor. The apparatus shown in Fig. 27 includes also a disk I28 having diaphragm openings of various sizes, as shown in the detail view, Fig. 29. The disk may be controlled by a magnetic or electromagnetic mechanism I29 similar to either of the mechanisms shown in Fig. 28 or 31, in order to place openings of different sizes in front of the cone I30 of the vaporizer I3I. In normal operation the disk I28 will be placed first with its largest opening in front of the cone;

when a predetermined thickness of metal has been deposited on the plate being treated the disk will be rotated, as by means of current from the contact (Fig. 21) to place a smaller opening in register with the cone and the same action will be repeated by currents from the contacts 24 and 93 to effect further reduction and stoppage of the flow of vapor as the thickness of the deposited metal approaches and reaches its final value. The stoppage of the fiow of vapor may be effected either by means of the disk I20 or by the shutter I24, as explained above.

It will be understood that the cylinder or 'disk shown and described herein may be moved mechanically instead of magnetically, such mechanical means comprising, for instance, springs which may be wound up at the start-of the operation and which are arranged to drive the parts until the operation is completed. It

will also be understood that the quartz plates is also possible to deposit non-metallic substancesand particularly fused quartz. Such a deposit may be made by vaporization in a high vacuum, the crucible being filled with quartz and vaporized at a higher temperature than aluminum. The use of a quartz deposit is advantageous because of the similarity between the deposited layer and the plate; the layer has the same ab-- solute resistance to external agents, has the same thermal coemcient (approaching zero), and has the product d1 v1 sufficiently similar to the product do 120 of the piezo-electric quartz so that there is little reflection. In cases where these properties are not strictly required a similar deposit of oxides such as those used in certain glass compositions may be used.

Observation and control of the thickness of the deposit may be obtained by periodically (at short intervals) placing near the outer surface of the quartz plate a metal plate connected with an external electric circuit which will maintain the quartz under treatment in a state of oscillation. While the metal plate is being applied it forms both a capacity and a screen to temporarily stop the deposit of vaporized material. The duration of such periods of measurement of the natural frequency can be reduced to a minimum compatible with the inertia of the relays shown in' Fig. 21, and the total duration of such periods may be made negligible in comparison to the total time of deposition.

An arrangement for effecting the control just referred to is shown in Figs. 32 and 33, wherein an insulating support I32 is mounted on the wall of the vacuum chamber to support the axis I33 which is electrically connected by the wire I34 with an external circuit for excitation of the quartz plate I35. A plate I36 is pivotally mounted on the axis I34 and is provided with arms I31 of magnetic material. The plate I36 also supports a capacity I38 which may have a shape similar to that of the quartz plate but be of larger size and may be made of a non-magnetic material. The capacity I38 may be provided with an insulatin finger I39 to prevent electrical contact with the cylinder or disk on which the plates are mounted, and the capacity may, if desired, have its face covered with a thin layer of insulation. On the outside of the wall of the vacuum chamber is mounted a system of magnets having a common armature I40 of soft iron with four cores I iI, I42, I43, I44 having their respective coils I45, I46, I41, I48. These coils are connected to a rotary contactor, not shown, which successively energizes pairs of cores as follows: First, MI and I42, forming a magnet which retains the arms I3! in their extreme position opposite these cores; then cores I42 and I43, holding the arms It! in the intermediate position shown in the drawing; and next, the cores M3 and I 54, holding the arms I31 in their opposite extreme position. The pivoted parts I36, I31, I38 are thus reciprocated into and out of the position shown in the drawing, the contactor being so operated that the capacity remains in front of the quartz plate only for a very short time, sufficient to observe the frequency of the plate. At other times the capacity remains in its extreme positions in which it does not stop the passage of the jet of vapor. A uniform deposit of material is assured by the symmetrical arrangement resulting from the use of the four magnetic cores described, and the insulating finger Its assures proper space between the capacity and the quartz plate.

If the quartz plate is so mounted that there are projections at its edges or corners (as in Figs. 18 and 19) the capacity may be shaped as shown in Fig. 34 so that the part I49, which is slightly smaller than the quartz plate, may be brought close to the surface of the plate while avoiding the projecting parts of the mounting. It would also be possible to obtain similar results by the use of a hinged capacity and shutter moved into and out of position adjacent the quartz plate by magnetic means.

It will be understood that various changes may be made in the form, construction and arrangement of the several parts without departing from the spirit and scope of my invention and hence I do not intend to be limited to the details herein shown and described except as they may be included in the claims.

What I claim is:

1. An apparatus for the manufacture of piezoelectric elements comprising, a vacuum chamber, a vaporizer adapted to project a jet of vaporized material into said chamber, a cylindrical support for a plurality of piezoelectric plates in said chamber, means for mounting said plates on the outer surface of said support, operating means for causing the rotation and axial displacements of said support, whereby the plates mounted on said support may be moved into and out of the vapor jet.

2. An apparatus according to claim 1 in which the operating means and the support are connected by magnetic fields through the wall of the vacuum chamber.

3. An apparatus according to claim 1 in which the means for mounting the plates on the support comprise magnets on the support and pieces of magnetic material engaging the plates.

4. In an apparatus for the manufacture of piezoelectric elements, a vaporizer comprising, a crucible adapted to contain a quantity of vaporizable material, a container tube of amorphous quartz containing the crucible and spaced therefrom by a vacuum space, a mirror on the inner surface of the container tube facing the crucible, high frequency induction coils disposed around the container tube and adapted for inductive heating of the material in the crucible to vaporize said material, and a restricted opening at the exit of the crucible for determining the size of the jet of vapor passing out of the crucible.

5. An apparatus for the manufacture of piezoelectric elements comprising, a vacuum chamber, a vaporizer adapted to project a jet of vaporized material into said chamber, a movable support for a plurality of piezoelectric plates in said chamber, means outside the chamber for operating said support to move the plates successively into and out of the vapor jet, and automatic electric means for actuating the operating means in accordance with the amount of vaporized material deposited on the plates.

6. In an apparatus for the manufacture of piezoelectric elements, a vaporizer adapted to project a jet of vaporized material for deposit on a plate of piezoelectric material, a high frequency electric circuit resonating at the natural frequency of the combined plate and deposited material, a high frequency electric circuit resonating at a standard frequency, means for deriving from said circuits a beat frequency resulting from the difference between said first-named frequencies, and means responsive to the beat frequency for controlling the deposit of material on the plate.

7 An apparatus according to claim 6 in which the means responsive to the beat frequency is adapted to reduce the rate of deposit of material as the beat frequency becomes lower and to stop said deposit when the beat frequency reaches a predetermined minimum value.

8. In an apparatus for the manufacture of piezoelectric elements, a vaporizer adapted to project a. jet of vaporized material, a support REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name Date Warner Mar. 29, 1927 Sommer Mar. 16, 1937 Bieling July 12, 1938 McLeod Oct. 28, 1941 Dom Feb. 24, 1942 Meeker Feb. 1, 1944 Ullrich Feb. 20, 1945 Richards et al Dec. 25, 1945 Dimmick Nov. 26, 1946 Ostenberg et a1 Feb. 18, 1947 Turner et al Dec. 16, 1947 Chilowsky July 20, 1948 Lange Nov. 9, 1948 

